1Department of Orthopaedic Surgery, William Beaumont Army Medical Center, Texas Tech University Health Sciences Center, 5005 N. Piedras St, El Paso, TX 79920, USA
2Statistical Consulting Laboratory, University of Texas at El Paso, Bell Hall 131 El Paso, TX, 79968, USA
3Department of Orthopaedic Surgery, Brigham and Women's Hospital, Harvard Medical School, 75 Francis Street Boston, MA, 02115, USA